Field of the Invention
The present invention relates to an acoustical-electronic component that operates with acoustical surface waves, including a piezoelectric substrate in which an acoustical surface wave is guided, and an electron system entering into interaction with the acoustical surface wave. The invention also relates to a tunable delay line, a resonator and a semiconductor sensor using the component.
Fundamental principles of interaction effects between acoustical surface waves and semiconductor electron systems are known from the publication: Physical Review B, Vol. 40, No. 11, Oct. 15, 1989, pp. 7874-78875. In particular, that reference discusses acoustical surface waves on GaAs/Al.sub.x Ga.sub.1-x As heterostructures. Especially the interaction between acoustical surface waves and quasi-two-dimensional inversion electron systems in strong magnetic fields and at low temperatures are investigated. It is pointed out that the interaction between acoustical surface waves and highly mobile quasi-two-dimensional electrons leads to a relaxation mechanism. That interaction is evidenced through strong quantum oscillations both in the surface wave intensity and in the speed of sound, which reflect quantum oscillations in the magnetoconductivity of the quasi-two-dimensional electron system in strong magnetic fields.
Surface wave arrays on GaAs and Si that are compatible with integrated circuitry are known, for instance, from the publication: IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-29, No. 12, Dec. 12, 1981, pp. 1348-1356 or the publication: IEEE Transactions on Sonics and Ultrasonics, Vol. SU-29, No. 5, September 1982, pp. 255-261. Those publications point to the possibility of realizing tunable SW resonators, tunable GaAs SW oscillators, monolithic SW convolvers and asynchronous SW correlators/programmable signal-adapted filters. However, in the first of those references, only high-voltage systems based on Schottky diodes are disclosed, which work at substantially higher, chip-incompatible and VLSI-incompatible voltages. Moreover, the blocking currents that unavoidably occur in that implementation represent a considerable problem in the power limitation of the component. Systems are known from the second of those references, in which a phase shift of the surface wave can be tuned through the voltage-controlled thickness of a depletion layer. However, that involves a volume effect, in which the maximum interaction between the surface wave and the mobile charge carriers is frequency-dependent.